An 8-year-old autistic boy died this week at a Bronx hospital, and investigators are probing whether malnutrition was a factor, according to cops and police sources.

Joseph Barney’s mother rushed him from their Williamsbridge home to Montefiore Medical Center Tuesday afternoon in an Uber, cops and sources said.

Cops responded to a call from the emergency room around 2:10 p.m. and found the boy unconscious and unresponsive. The boy, who had no obvious signs of trauma, was pronounced dead at the hospital.

Joseph was only 30 pounds when he died, police sources said. According to CDC figures, the average 8-year-old should weigh around 50 pounds.

His 29-year-old mother informed cops he was autistic and non-verbal, cops said.

The mother and her 32-year-old boyfriend were at one point questioned by authorities — though it was unclear whether the questioning was ongoing Wednesday afternoon, cops said. 

No one has been arrested.

Video footage viewed by a neighbor, who declined to give his name, shows the couple leaving the home with the boy. 

“A dark-colored car drove up and the lady came out,” the neighbor said. “She came down the stairs and approached the driver from the front passenger side.”

“A guy came out with the child while she was speaking with the driver,” he added. “The child’s legs were hanging down and the head was hanging down over his shoulder. The legs were dangling, like limped. The whole body looked limp. He pulled shut the door behind him and came down the stairs with the child.”

“He cradled the child’s head as he went in the car,” he said. “They got in the back of the car with [the] child and drove away.”

Neighbors said they had never previously seen a child in the home. 

“I’ve never seen the kid,” another man said. “I’ve never heard the kid cry. I never knew there was a kid over there.”

The boy’s cause of death remains under investigation by the city medical examiner’s office.